This invention relates generally to a strip of thin resilient plastic material including a plurality of longitudinal rows of bands for receiving a plurality of rows of containers.
The invention more specifically relates to a carrier stock for machine application where stretching forces for applying the strip to the rows of containers is nonuniform relative to either the longitudinal axis of the strip stock or to the lateral axis of each rank of container receiving bands.
Heretofore, container stock of the type generally described has been symmetrical about the axis of the stock and the axis of each laterally aligned rank of bands. Typical symmetrical carriers are shown in U.S. Pat. Nos. 2,874,835; 3,711,145; 3,874,502 and 4,018,331.
Furthermore, the carriers typified by the above patents have been utilized with machines, such as shown in U.S. Pat. No. 3,383,828, or which use a pin for gradually and continuously snapping the carrier strip bands beneath the chimes of cans without substantial stretching or with machines, such as shown in U.S. Pat. Nos. 3,221,470; 3,775,935; 3,816,968 and 3,959,949 which use jaw-like stretching members arranged about a rotating drum designed to gradually stretch each aperture a desired amount so that the bands may be snapped beneath the chimes of the associated container. In these rotating jaw-type machines, the stretching forces to be absorbed by the carrier strip are generally uniform in that a pair of opposing jaws that are either applied to the strip or to each individual aperture are both moving relative to one another as the drum rotates. Thus, a high differential stress situation on the carriers is not encountered with these machines.
However, with the advent of different machine applicating techniques incorporating different stretching forces to be absorbed by the carrier strip coupled with the desire to use a thinner gauge material and less material in the carrier, the problems of concentration of stress forces or differential loading during carrier application become important. For example, new machine concepts, such as those typified in U.S. Pat. No. 4,111,135 and U.S. Ser. No. 59,019 may create a localization of stress in certain regions of a thin carrier strip and which may be detrimental to both the application and to the resulting package. Both of these two machine concepts apply relatively uneven stretching force to the carrier strip when compared with the above-noted prior art techniques. In the first mentioned new machine concept, each rank of container encircling bands is stretched through the use of solely the containers themselves in a manner which creates more stress in certain regions of the rear area of bands than in the corresponding front areas of the same bands. Likewise, the second mentioned new machine concept utilizes a rotating drum in which a plurality of pairs of jaws include only a single moving jaw member and single stationary jaw to stretch an entire rank of container encircling bands. Thus, the band which is associated with the moving jaw tends to move more and is subject to a higher stress than the band which is associated with the stationary jaw.